1. Field of the Invention
The present invention relates to a method of purifying nanodiamond powder and highly-purified nanodiamond powder.
2. Description of the Related Art
Nanodiamonds are used as abradants because of their hardness, and they can also be used as an insulating material, an optical material, and a biomedical material.
In WO2007/133765, Gogotsi, et al. disclosed an oxidization process to remove sp2 carbon from commercially available nanodiamond powder. However, a small percentage of sp2 carbon can still be detected after the oxidization process. In addition to the removal of sp2 carbon, metal impurities might be an issue when the nanodiamonds are used as an optical or biomedical material.